A basic cellular phone plan costs $ 18 per month for 50 calling minutes. Additional time costs $ 0.90 per minute. The formula Upper C equals 18 plus 0.90 left parenthesis x minus 50 right parenthesis gives the monthly cost for this plan, C, for x calling minutes, where x greater than 50. How many calling minutes are possible for a monthly cost of at least $ 63 and at most $ 72 question mark

There is a possibility of at least 100 calling minutes and at most 110 calling minutes.

Step-by-step explanation:

The given equation in words from the question is: C = 18 + 0.90 (x - 50)

This gives the formula for the Monthly Cost for the plan, C

The aim is to find the possible number of call minutes for the cost between $63 to $72.

So, we solve this first equation for the value of "x", putting C = $63

18 + 0.90 (x - 50) = 63

0.90 (x - 50) = 63 - 18 = 45

x - 50 = = 50

x = 50 + 50 = 100 calling minutes

Next, we put C = $72, so that we have;

18 + 0.90 (x - 50) = 72

0.90 (x - 50) = 72 - 18 = 54

x - 50 = = 60

x = 50 + 60 = 110 calling minutes

So, for a monthly cost of at least $ 63 and at most $ 72, there is a possibility of at least 100 calling minutes and at most 110 calling minutes.